Author Topic: Tyre pressures  (Read 703 times)

Offline mistac

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Tyre pressures
« on: 27 March 2021, 20:30 »
When i got my GTI a year ago, I set the pressures to 36psi (from memory). I must admit I tend to get a bit lazy and just wait for the TPMS to flag up any pressure issues. Today, out of the blue I got a "front left tyre pressure low" warning so checked all the pressures. They were all down and ranged from the lowest reading (front left) at 29.5psi to 32ish psi on the others.

I have two questions

1. I didn't realise the TPMS indicated which tyre had flagged the warning - although it did not say the actual reading, I thought it just flagged a global warning that a tyre (or tyres) were low ?
2. I thought there was a certain % allowance before the TPMS warning came up, but dropping from 36psi to 29.5psi seems a larger drop than I would have thought before the warning came up?

I have therefore learnt I need to check my tyre pressure far more regularly. The other thing is I have been a little disappointed for a while now about the fuel economy as most of the time we drive pretty normally in  "normal" and D". I know its obvious but having increased the tyre pressures to more or less the correct level, the economy already seems to have got better!   
« Last Edit: 27 March 2021, 20:32 by mistac »
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Offline barrym381

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Re: Tyre pressures
« Reply #1 on: 27 March 2021, 20:43 »
From memory I don’t think the warning appears till they drop below 30psi

Offline fredgroves

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Re: Tyre pressures
« Reply #2 on: 27 March 2021, 21:19 »
It doesn't know anything about the actual tyre pressure, it's based on data from the abs sensors.

It detects a problem by one tyre rotating differently from the others. There probably is a value you could assign to how low it needs to be to trigger that but it's simply a weird abs signal that triggers it.

As you can see though if all of them are down it won't detect that at all.

And yes tyre pressure does effect fuel economy simply by increasing the contact patch so more resistance.
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Offline Finglonga

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Re: Tyre pressures
« Reply #3 on: 27 March 2021, 21:47 »
Ideally you should be checking them weekly when you check the oil, coolant and top up the washer bottle as pressure also makes a huge difference to tyre wear. As said they don't go on pressure it is all about the ABS sensors picking up discrepancies in rotation.

Offline Kpow99

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Re: Tyre pressures
« Reply #4 on: 28 March 2021, 07:25 »
Also check the pressure at night or first thing in the minoring as ambient temp will affect pressure.

Tyre pressure levels are set for cold tyres. A long run to a garage to top up won’t help as they will heat during the ride there.
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Offline Yusee

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Re: Tyre pressures
« Reply #5 on: 28 March 2021, 09:43 »
I check around once a month and usually have to top up 1-2 psi each tyre.
I also log a note in my mobile of when I have checked levels in my 3 cars.
« Last Edit: 28 March 2021, 09:45 by Yusee »
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1988 Peugeot 205 GTI 1.9